This invention relates to a drill section of a drilling tool and, more particularly, to a drill section in which tool joints may be replaced without reducing the length of a hollow tube of the drill section.
In a drilling tool used for drilling holes in the ground in oil fields, for forming water wells, and for forming blast holes to enable disposition of explosives in the ground in the mining industry, the drilling tool is formed by a plurality of drill sections connected to each other. Each of the drill sections includes a steel hollow tube having a threaded pin joined to its upper end by a circumferential weld and a box attached to its lower end by a circumferential weld. The threaded pin has a tapered-threaded pin extending from its end while the box has a tapered threaded recess to receive the tapered threaded pin of the next lowermost of the drill sections of the drilling tool. Each of the threaded pin and the box may be deemed to be a tool joint.
The lower end of each drill section of the drilling tool receives the most wear of the two ends because of the upward movement of debris produced by cutting by the drill bit at the bottom of the drilling tool. This lower end of the drill section is the end of the drill section having the box.
When wear of the box by debris requires replacement of the box or either the box or the threaded pin breaks and must be replaced, the drill section must be removed from the remainder of the drilling tool, and both ends of the hollow tube of the drill section are then cut off. Both ends of the hollow tube are cut off because maximum benefit is obtained by alternate switching of the ends of the hollow tube of the drill section to which the box and the threaded pin are attached.
The new box would be welded to the bottom tube with its length equal to the length of the replaced box and the removed portion of the hollow tube. The new threaded pin would be welded to the bottom tube with its length equal to the length of the replaced threaded pin and the removed portion of the hollow tube. Thus, the overall length of the drill section remains the same.
A relatively long period of time is required to remove the drill section from the string of drill sections forming the drilling tool. This can result in reduced production for that specific day.
Furthermore, if the drilling tool is drilling blast holes to receive explosives as is required in the mining industry, the failure of the drill section can have an effect on the blast pattern. This is because federal law prevents explosives, which have been disposed in the blast holes, from being left overnight. Therefore, some of the blasting would have to occur one day and the remainder the next day because explosives are placed in the blast holes before all of the blast holes are completed. This could result in it being more expensive to remove the debris such as rock, for example, from the premises than if all of the blast patterns were completed.
The drill section of the present invention satisfactorily solves the foregoing problems through providing a drill section in which it is not necessary to remove both ends of the drill section from the string of drill sections. Instead, it is only necessary to remove the one end of the drill section having the worn or broken tool joint to be replaced from the remainder of the drilling tool.
Additionally, the drill section of the present invention does not require the removal of any of the length of the hollow tube of the drill section. Thus, the length of the hollow tube of the drill section of the present invention is not shortened as occurs with presently available drill sections.